Advantageously, the composition can act as paint primer, finding very diverse applications for which the provision of coatings providing good protection against corrosion phenomena has been induced.
In this field, currently agents such as chromates are used as they are powerful oxidizing agents and thus also effective antioxidants for surfaces which they protect in the presence of water and oxygen. They are used as anticorrosive pigments in organic formulations (paints) and are not very soluble in water.
Nevertheless, chromate salts are harmful due to their high oxidizing power and have to be replaced with other substances having weaker but less toxic antioxidant properties.
Generally, a paint applied to a metal ceases to be effective when an injury occurs at the surface. Water, in combination with atmospheric oxygen and atmospheric pollutants, then begins the process of corrosion of the metal, for example based on aluminum or iron.
In order to reinforce the protection of a metal surface to be coated, a first treatment, referred to as surface pretreatment, is generally carried out in the presence of surface treatment agents which are chemical agents which modify the surface to be coated in order to protect it.
At the same time, an adhesion primer or paint primer based on solvent, on resin, on catalyst and on inorganic fillers, including an entity known as anticorrosive pigment which is intended to reinforce the protection against corrosion of the surface which will be coated with it, is prepared.
Conventionally, this adhesion primer is deposited on the pretreated surface and then said primer is dried before carrying out the deposition of a paint finishing layer.
While the pretreatment operation is carried out in the presence of an aqueous solution, the operation of coating the adhesion primer is carried out in the solvent phase, the combined operations thus comprising two types of operations in different media.
Starting from this context and from all the parameters present, the applicant turned to the principles of encapsulation and of controlled release in order to enhance the performance of a functional agent. This concept has already been provided in various forms in fields as diverse as perfumery, detergency, medicine, medical imaging, cosmetics or food.
Generally, a colloidal vector provides effectiveness if it is capable of protecting the active principle as far as the site of delivery. In medicine, a well-known example relates to the passive capture by tumors of 50 nm colloids; if these colloids contain an active substance, it is naturally found enriched in the region to be treated. In industrial perfumery, for example, it will be a matter of prolonging the odor after opening the pack.
Thus, the applicant started from the principle that capsules of antioxidants should be able to deliver their contents locally in order to consume this oxygen while if possible repairing the injury in addition and provides a novel solution of a composition incorporating a hydrophilic phase including the surface treatment agent in an organic continuous phase.
In the field of paints, generally, the inclusion of a surface treatment agent has the objective of reproducing as best as possible the same properties as a conventional surface treatment of conversion treatment type. Its main role is the adhesion, which consequently makes possible better resistance to corrosion of the primer. The surface treatment chemical agent exhibits a solubility in aqueous solution of approximately 100%.
The anticorrosive pigments for their part make it possible to reduce the rates of corrosion. The water which pierces the film of paint will dissolve a portion of the pigment which, at its contact, forms impermeable screening precipitation compounds which prevent the water, the oxygen and the salts from reaching the metal. The anticorrosive pigment for its part exhibits a very low solubility in aqueous solution which can typically be of the order of a few ppm.